The present invention relates generally to a device and method for identifying a container and, more particularly, to a device and method using the slot of the container as an antenna for remote communications.
It is often necessary to monitor the location and movement of materials within a distribution center or manufacturing facility. One method of tracking the materials is to attach a wireless communication device such as a radio frequency identification (RFID) transponder or other identification device to containers that are housing the materials. By way of example, a liquid container such as a barrel or keg may include an identification device indicative of the liquid contained inside. An interrogation reader, or series of receivers, having an antenna device and able to send information remotely through electronic signals, is placed throughout the distribution or manufacturing facility to receive signals transmitted from the identification devices. The signals are then passed to a central control system that monitors and records the applicable information. The central control system can also send information to its interrogation readers to send to the transponders for response and/or to be stored in the transponder""s memory.
The information communicated by the containers in the system to the interrogation readers may be used for a number of reasons. For example, a statistical analysis may be made of the materials to maintain an accurate inventory, production flow rates, and other production standards. Additionally, the identification devices may include specific information about the materials housed within the containers including date of manufacture, place of manufacture, type of product within the container, temperature of the container and ambient air, temperature of the contents of the container, and pressure of the container, etc. The wireless communication device must have some type of antenna arrangement to communicate information about the containers to the interrogation readers. It is generally known for wireless communication devices to include an antenna. It is often a problem for many wireless communication devices to provide antenna especially if the wireless communication device is small or is required to be placed in a contained area. The length of the antenna must be tailored to the specific frequency that the wireless communication device is designed to operate. For low frequencies in the megahertz range or lower, an antenna may have to be several inches long to several feet long. Even for higher frequencies, the antenna may have to be several inches long to allow successful communication at the desired operating frequency.
Additionally, the antenna must either be packaged inside the wireless communication packaging or located external to the wireless communication device. External positioning of the antenna to the wireless communication device provides several other challenges when placing the wireless communication device in confined areas such as a container. The antenna may have additional problems radiating energy effectively if the antenna is contained internal to a device such as a container.
One example of a container that one may wish to attach a wireless communication device to is a beer keg. A beer keg has a substantially cylindrical shape with a smooth, uniform outer wall. There are no extensions or areas for effectively attaching the wireless communication device. Even if the wireless communication device can be attached to the keg, additional problems in packaging and unaltered communication exists in including an antenna for the wireless communication device as described above.
Some containers have a slot as a characteristic of their manufacture. For example, a beer keg is made out of a metal material that has an outer wall with a curled end to form a rim. The keg rim is used for handling and movement of the keg. The curled portion of the rim bends inward towards the outer wall leaving a small gap between the edge of the rim and outer wall. This small gap forms a slot that extends circularly around the keg and can be used to provide a slot antenna for the wireless communication device. The wireless communication device can be designed to provide electronic connectivity to the slot when installed so that the slot can be used to provide the effect of an antenna. Since the slot of the container may be several feet long, using the slot for the antenna may be advantageous for communication at lower frequencies where providing an antenna of sufficient length for communication at the desired frequency is problematic.
Therefore, it is advantageous to use the slot of a container to provide an effective antenna for a wireless communication device.
The present invention includes a wireless communication device using a slot antenna arrangement formed by the slot of a container. A wireless communication device is provided with the container to provide information about the identification or other aspect of the container as it moves through manufacturing, tracking or shipping facilities.
An antenna is provided for the wireless communication device so that it can communicate remotely with a transmitter/receiver sometimes called an interrogation reader. The present invention capitalizes on the phenomenon that exists whereby a slot cut out of a conductive material such as metal can be coupled to a wireless communication device""s communications electronics to provide the effect of a pole antenna.
Some containers have by the nature of their construction a slot that can be used to provide a slot antenna. Alternatively, a slot can also be cut out of the container as well. Using a slot antenna instead of a pole antenna provides several advantages. The length of the slot for the wireless communication device to operate at the desired frequency may be more suitable than could be provided by using a pole antenna. Additionally, the slot does not require that a pole device be placed inside or proximate to the container. This is especially true for lower frequency communications that require longer length antennas. Using the slot may also be less expensive than using a pole antenna. Additionally, a pole antenna may extend from the container that may expose it to damage.
In one embodiment, the wireless communication device uses feed lines directly connected to the each edge of the slot.
In another embodiment, the wireless communication device includes feed lines that reactively couple with each edge of the slot.
In another embodiment, a conductive device is placed between the slot to couple the wireless communication device to the slot and provide the slot antenna.
In yet another embodiment, the wireless communication device is mounted on a non-conductive substrate in the slot. A feed line from the wireless communication device rests on the substrate such that it reactively couples with the slot to provide the slot antenna.
A technique is provided to ensure that the operating frequency of the slot matches the operating frequency of the wireless communication device to maximize the slot antenna radiation efficiency. A circuit is provided in between the slot and the wireless communication device to match the impedance of the slot to the impedance of the wireless communication device.
In an alternative embodiment, shorting posts are provided on the ends of the slot to create a slot with the desired length. The shorting posts are constructed out of a conductive material and are placed between the slot""s edges to short both sides of the slot together.
The invention also includes a method of monitoring the container. While the container is within a facility, such as during manufacturing, filling, or storing, the container is moved through at least one interrogation point containing an interrogation reader. Communication between the wireless communication device and the interrogation reader is established for monitoring the location and/or content information about the container. A central control system may be in communication with the interrogation point for monitoring the movement of the container. The central control system may monitor the position of the container, or it may also monitor specific information that is stored within memory in the device.